This invention relates to an electromagnetically actuated needle selector for circular knitting machines such as those for the production of hosiery, and with the possible capability of creating patterns on the knitted fabric under electronic control.
GB No. 2138847-A published Oct. 31, 1984 and JP No. 61-47856-A published Mar. 8, 1986 are hereby cited as the prior art that is believed to be closest to the instant invention. The former application suggests a needle selector including an upright knitting cylinder carrying multiple needle jacks slidably received in as many grooves cut longitudinally in its surface. The needle jacks are to be selectively raised for creating patterns on the fabric being knitted.
For selectively lifting the needle jacks on the knitting cylinder, the application first cited employs a vertical stack of L-shaped selector levers pivotable about a common vertical axis. Each selector lever has a twisted tip at one end for engaging and pushing up the butt of each selected needle jack and carries three permanent magnets in a horizontal row on the other end. Disposed adjacent to said other ends of the selector levers are pairs of electromagnets forming a vertical row. As each pair of electromagnets are alternately excited in opposite directions, the corresponding selector lever is swung back and forth by the attractive and repulsive forces exerted between the pair of electromagnets and the three permanent magnets on the selector lever. The twisted tips of the selector levers will then act on the butts of the needle jacks on the knitting cylinder, which rotates at high speed, to lift the desired needles.
An objection to this prior art needle selector is the large vertical dimension necessitated by the vertical stacking of the pairs of electromagnets. Furthermore, since the self-excited vibration of the electromagnets upon energization, is transmitted directly to the needle jacks via the selector levers, the prior art device generates considerable noise and vibration and the twisted tips of the selector levers are subject to rapid wear. Such vibration is all the more objectionable because it impedes the positive actuation of the selector levers, and hence of the needle jacks, by the electromagnet pairs.
The second mentioned application teaches the use of intermediate drive members which are driven by pairs of electromagnets and which in turn drive selector levers capable of engaging with butts on the needle jacks. The vertical dimension of this second prior art needle selector must also be of necessity so great as to cause inconvenience in handling the bobbins in the use of the knitting machine. Moreover, the construction of this known device is very complex, making its manufacture and adjustment difficult.